This invention relates to a method for inserting a tube into a borehole in the ground according to the introductory portion of claim 1. This invention further relates to an installation for inserting a tube into a borehole in the ground according to the introductory portion of claim 18.
Such a method and installation are known from U.S. Pat. No. 3,677,345.
In the use of such a method and installation, for instance for drilling or lining a drilling well for extracting minerals, tube parts are successively coupled through a screw coupling to the upper end of a tube reaching into the borehole. As the tube is introduced further into the ground, tube parts are successively added by coupling them to the tube.
An inherent disadvantage is that the couplings occupy space, so that the outside diameter of the pipe adjacent the couplings increases while the inside diameter remains the same, or the inside diameter decreases while the outside diameter remains the same. Moreover, the couplings are fragile and sensitive to wear, and must be tightened with accurately controlled couples, on the one hand to ensure a proper joint and sealing and, on the other, to prevent overloading of the coupling halves.
It is also known first to form a tube by rolling a strip of material lengthwise into a tubular form and welding it along a longitudinal seam. The tube is wound onto a reel. When installing the thus obtained tube, the reel is unwound. A disadvantage of this method is that in order to obtain a reel that can be handled at all, the tube needs to be bent strongly, whereby it is subjected to strong plastic deformation when being wound onto the reel. This has an adverse influence on the mechanical properties and the geometry of the tube. Nor is this method suitable for installing concentric tubes.